Which GI wall layer is primarily responsible for peristaltic movements?

• A. Mucosa
• B. Submucosa
• C. Muscularis
• D. Serosa

Answer: (C)

Peristaltic propulsion is produced by the muscularis externa, the GI wall layer that contains smooth muscle arranged in an inner circular layer and an outer longitudinal layer. When these smooth muscles contract in a coordinated, wave-like fashion—driven by the myenteric (Auerbach) plexus—contents are pushed forward along the tract. The mucosa lines the lumen and handles secretion and absorption, not movement. The submucosa provides support and houses vessels and the Meissner plexus that regulates local secretions and blood flow. The serosa is the outer protective covering. So the muscularis is the driver of peristaltic movements.